Field of the Invention
The present invention relates to wireless communication, and more particularly, to a method of detecting a synchronization reference signal from a neighboring terminal when a terminal to which a V2V technology is applied is located out of coverage of a base station and thus cannot receive a synchronization signal from the base station.
Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved from the 3GPP LTE.
In LTE/LTE-A, a physical channel of LTE may be classified into a downlink channel, i.e., a PDSCH (Physical Downlink Shared Channel) and a PDCCH (Physical Downlink Control Channel), and an uplink channel, i.e., a PUSCH (Physical Uplink Shared Channel) and a PUCCH (Physical Uplink Control Channel).
There is a need for communication between pieces of UE located at a physically close distance, that is, device to device (D2D) communication, due to an increase of user needs for social network service (SNS).
D2D communication may be performed between pieces of UE located in coverage of a base station or may be performed between pieces of UE located out of coverage of the base station. Furthermore, D2D communication may be performed between UE located out of coverage of a base station and UE located in coverage of the base station.
Contents regarding D2D may be applied to vehicle-to-everything (V2X). V2X generally refers to a communication technology through a vehicle and all of interfaces. An implementation form of V2X may be various, such as vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-person (V2P), and vehicle-to-network (V2N).
Meanwhile, the aforementioned V2X technology directly uses a sidelink (i.e., D2D communication) technology. However, as a technology for a vehicle or the like, the V2X is applied to a terminal which moves with high speed in comparison with D2D communication. Therefore, there is a problem in that the existing 3GPP standard is not appropriate to an example of implementing V2V communication.